Contrary to the advice I’ve been accustomed to getting.
Your OP clearly establishes that as matters stand your work has no value to anyone but you - even your own family aren’t interested. This means once you die and you are not around to preserve it, it will be trashed unless you can somehow give it value to others or at least appear to. One way is fame which will give your work value and you are pursuing that. Another is to legally tie your valueless work to something of value. Others have suggested the means - some sort of endowment arrangement.
Another possibility is to cheat and try to give your work the appearance of value it doesn’t have. You could rename your digital works with names that make them appear to have value so that people will pass them around. Illicit porn (child porn etc) has substantial value (unfortunately). Rename your files suitably with keywords that will cause people to mistakenly think that your work is as valuable as illicit porn and it may well be possible to cause the files to travel around through private porn collections shared through the dark web for an extended period.
Of course anyone who opens them will discover the files don’t have the value they thought, but AIUI that may not stop them being passed around endlessly as part of large caches of porn for an extended period.
Edited to add: I just remembered another element of this suggestion (which isn’t original). Name your files “something interesting [part 2].mpg” or whatever and issue parts 2-12 (or as required) but don’t issue part 1. People will keep the other parts hoping to find the elusive part 1. But never will.
“Anyone who says they want to live forever doesn’t know what it’s like to get old.”
My father had a hobby of creating metal sculptures, mainly from scrap he found along railroads and abandoned structures around the western Nevada desert, when we lived in Reno for a few years when I was growing up. He sold most of his work somehow (before craigslist), perhaps thru friends and word of mouth, so we did not have a backlog of sculptures sitting around.
After he died I inherited the few pieces he still had, and I have kept 4-5 of them, but one was too big for my house and not really something I wanted - a large and attractive wall piece shaped like the state of Nevada - I live in California. I did not want to trash it, so searched for someplace to donate it. I remember it once hung on the wall of a bank, but no banks in Reno or Tahoe responded to my offers. Finally, one of the Visitor’s Bureau near Tahoe responded that they would gladly take the piece if I brought it to them (which I did after a day of skiing). It’s been hanging proudly in one of their visitor centers for years now (I went back recently and it’s still there). I think dad would be pleased.
Anyway, if you keep your physical art in a closet, no one will ever see it, appreciate it, or know it’s there, and it will remain value-less. As someone else said here, a thing is only worth whatever value someone else puts on it, not what you think its worth. If you want your art remembered, just give it away, maybe to public institutions like the library or city hall, or a school or university.
As for the digital stuff, maybe share it on social media or the internet somewhere - it’s rumored anything posted there will last forever. Maybe create a thread here on SDMB posting your work. Sadly, us, and everything we create, will eventually end up underground.
I buy meat from heritage breeds of pig and turkey. Part of the sales pitch is “help preserve this now rare breed.” This is absolutely a thing that’s done with rare breeds of domestic animals. I think that makes a lot of sense.
Similarly, art that has value to someone is much more likely to survive. When we cleaned out my mom’s apartment, we kept the art we liked, and sold the art that could be sold, and threw away the rest.
Can you build a market for your art? The easier it is to sell, the more likely it is to survive.
Giving it to a local university is also feasible, but why put all your eggs in one basket?
Given you stated goals, maybe I should invest early!
Harking back to my initial suggestion about endowing an institution with some intent about keeping the work. There is a growing understanding in many areas of the need to preserve recent history. A huge amount of effort is going on around the world to capture, digitise or whatever, but more importantly catalogue, curate and maintain history. Where history is anything up to right now. Preserving current artists works is clearly within the remit of such efforts, along with all the other work going on.
I feel pretty sure that a bequest to help local efforts in preserving art history would be welcome. If it just happened that your own work was directly in line with the preservation goals, well that is a nice win.
In general we have been terrible at preserving the just passed history. We throw out stuff that is a couple of decades old as simply unwanted clutter. Another couple of decades and there is a muttering of interest, and a few decades more and there is significant interest and a great deal of moaning about how much has just gone forever. A lot of the stories above exemplify this effect. People don’t value the familiar but old. Give it another few decades and they will deeply regret what when to landfill.
Copyright it.
Either as individual photographs or, if you want to save money on fees, create a book of photographs and copyright the book.
It will be preserved for as long as the U. S. Library of Congress exists, perhaps longer, by some successor entity. Maybe not forever, but probably a few hundred more years, and at no cost to you or anyone else except U. S. taxpayers.
Now, it may not be as accessible as you would prefer. I don’t happen to know if the LOC allows people to see any work that has been registered for copyright. But there would be a record of it, and it would be preserved.
Another possible snag: Does the LOC keep the registration copies of works that have fallen out of copyright indefinitely, or does it dispose of them at some point?
I came here to post: The SDMB is your best chance to achieve immortality, but you ninja’d me! 
Your fate is in Cecil’s hands. Cecil has the power to archive your deepest thoughts and feelings forever, making you immortal…or, he could reformat the drive you reside on and turn you into digital dust. Best to keep your yearly membership payments up to date.
I started to mention something in my earlier post, but dropped it as a distracting aside. Since @Tibby just above has helpfully re-awakened this idea, I’ll add here now what I had considered saying there then.
It IS possible for anyone to easily get a backup of their entire SDMB posting history. Probably better to try this on a computer, not a tablet or especially not a phone.
Click your avatar to go to your user page, e.g.
Select Preferences >> Account. Under the “Export your data” heading near the bottom click the [Request archive] button then [Yes] on the “Are you sure?” popup.
After maybe a minute you’ll see a green notification on your icon that you have a PM. In that PM is a url to a temporary zip file you can download. In the zip are several files, one of which is all your actual postings.
It’s not in the most user-friendly format, but anyone with a bit of tech skill and motivation can figure out how to extract and organize all your posts.
I wonder how long they would last if you encased them in very, very, thick glass blocks and buried them far away from earthquake zones and volcanoes.
Some future archeologist might dig one up and put it on display. Add some metal plates with explanations translated in various languages and it might become a new Rosetta Stone.
As this is really a request for advice, I’ve moved it to IMHO.
Until the cure for death comes along, you can extend your life indefinitely by not planning for the future, thereby living to regret it. It’s working so far!
This thread has given me a lot of good ideas, especially contacting some institution and asking if they’re willing to house my digital artifacts and also copyrighting the material.
It’s even given me an idea for a business, for which I’ll need a technologically gifted partner: why not start a service that arranges for a perpetual board (members to be replaced as they die off) that charges a fee for digital storage and cataloguing, marketed to artists, writers, composers, etc. who wish for their works to outlive them? I suppose we’d need multiple duplicative online venues (in case of tech disasters), cloud backup, etc. but that can’t be prohibitively expensive, can it? We’d need to build in enough profit to make serving on the board attractive, but again with enough subscribers shares in the company would be relatively cheap.
Of course if such existed already, I’d be glad to know of it, but since it doesn’t seem to, maybe I could start one. Anyone willing to partner with me?
Since neither you nor anyone else has commented on my suggestion of using copyright, what’s your objection to that?
It’s very inexpensive and probably far more permanent than any theoretical business/organization/entity that you or others have been proposing. And it exists now.
I just thought of a technique that would increase the likelihood of your works surviving longer: register them in several countries’ copyright systems. Although not necessary for copyright purposes – countries honor each other’s copyrights – registering in the UK, France, Japan, etc. would create multiple backups.
Using copyright may not make the works as accessible as you would prefer in your dream scenario, but it is available to you now with essentially no effort or expense, especially compared to the alternative of creating, de novo, an organization that is intended to exist and provide services “forever.”
ETA: I just noticed your mention of copyright in your last post. Still interested in your further thoughts.
I think it works beautifully, but especially as an additional service in my proposed digital storage and cataloging concept, as yet another way of preserving art. We could build it in as a recommended option, with a copyrighting fee to cover the additional costs. This way, my clientele would be multiply assured that their work will live into the future, supported by various online entities, each backed up on various clouds, and by copyright.
The New York Public Library (to whom I have no connections other than an expired library card) seems to have an extensive digital archive PDF about NYPL’s archives that I can make inquiries to. I don’t know if it will be persuasive to them that much of my work is set in NYC and was done there, but I keep asking what is the downside to them saying “Sure, send the files.” I can’t see one for them, even leaving aside my monetary contribution.
Person known to be the closest to living “forever” was 122 when she died.
Post on the Internet.
Hey! Look! You made it!